Lamp bulb coating apparatus



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hwveTvtOT-S: Alff-T'eci. L. Patme- Havotd G. Anderson bg /Z The .AFL-fl,- Tneg United States Patent O 3,324,824 LAMP BULB CGATIN G APPARATUS Alfred L. Palmer, Lyndhurst, and Harold G. Anderson, Kirtland, Ohio, assignors to General Electric Company, a corporation of New York Filed ct. 18, 1965, Ser. No. 496,881 Claims. (Cl. 11S- 47) The present invention relates to apparatus for applying a diffusing coating7 to the interior of electric lamp bulbs. More particularly the invention relates to apparatus for application of coatings by the combustion of an ethylsilicate compound to produce a silica smoke for depositingr a coating of extremely finely divided amorphous silica such as described and claimed in Patent 2,545,896 to Pipkin.

Attempts have been made over the years to provide an automatiically operating machine to coat bulbs in the stated manner. However, such machines have not met with commercial success. Accordingly, it has been the practice to perform the coating operation on manually operated bench units which comprise burners wherein tetraethyl orthosilicate is fed upwardly in a central tube, the upper end of which is heated to a temperature sulicient to vaporize the liquid silicate where it is mixed with oxygen and burned inside the bulb to produce a white fume or smoke of silica. The device requires the aid of operators who clean the burners and load and unload the bulbs. The prior art processes and equipment have required the use of tetraethyl orthosilicate which is relatively expensive compared to condensed ethylsilicate.

It is therefore an object of this invention to provide a machine of the character described above and which is fully automatic in operation and is considerably more economical than prior art devices. It is also an object to provide a machine which operates entirely satisfactorily with the less expensive condensed ethylisilicate which consists of tetraethyl orthosilicate and about to 15% by weight of polysilicates, for example, polyethoxy siloxanes.

Briey stated, in accordance with one aspect of the in- L vention, the apparatus comprises a continuously rotating turret type machine which carries a plurality of spaced burners at its periphery each comprising a fuel cup of a size to hold a predetermined amount of ethylsilicate fuel necessary to properly coat a single bulb. Provision is made for feeding the silicate fuel to the cups in the proper doses, for supplying a flow of oxygen around the cup to properly support combustion of the silicate vapors, and for igniting the vapors preparatory to placement of a bulb over the cup. In accordance with an important feature of the invention, provision is also made to assure that the fuel cup is at a temperature in the range of about 110 to 135 C. at the time the silicate fuel is fed thereto, whereby the silicate fuel is properly volatilized for uniform burning to provide a uniform coating of silica on the bulb walls. While the more highly purified tetraethyl orthosilicate may be used as the fuel, it is of course advantageous to use the less expensive but equally effective condensed ethylsilicate.

Further features and advantages of the invention will appear from the following detailed description of a species thereof and from the drawings wherein:

FIG. l is a top plan view of a machine comprising the invention;

FIG. 2 is a fragmentary section through one of the burner heads with a bulb in place thereon;

FIG. 3 is a fragmentary perspective, on a larger scale, of a burner head showing the fuel cup in an elevated position relative to the bulb supporting spindle;

FIGS. 4 and 5 are respectively, fragmentary side and front views of a portion of a silicate fuel feeding mechamsm;

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FIG. 6 is an elevation, in section, of the machine at a location where a bulb has just been fed or placed onto one of the burner heads;

FIG. 7 is a horizontal section through mechanism for cleaning the interior of the fuel cups;

FIG. 8 is a side view of brush arrangement for cleaning the outside of the burner and spindle; and

FIG. 9 is a fragmentary top plan view of a turret having a modified arrangement for rotation of the burner heads.

Referring to the drawings, the machine comprises a continuously rotating turret 1 which turns counter-clockwise as seen from above in FIG. l and which carries a plurality (twenty-four) of equi-distantly spaced burner heads 2 (FIG. 2) which are carried on individual brackets 3 mounted on the periphery of the turret. The turret 1 is mounted on a hollow column 4 (FIG. 6) which is rotated through a gear train 5, 6 driven from a speed reducer 7 which is driven by an electric motor (not shown). The burner in each head 2 comprises a metallic fuel cup 8 (FIGS. 2 and 3) carried by a metallic tube 9, each of which may be made, for example, of stainless steel. As here illustrated, the upper end of the tube 9 is capped or closed, the cup 8 is provided with a threaded lower end 1Q by which it is screwed into a tapped hole at the center of the capped top of the tube 9. The said top of the tube 9 is also provided with a plurality (four) of small longitudinal holes 11 which communicate with the hollow interior of the tube 9 for passage of oxygen and which are located close to the periphery of the cup 8. The cup 8 holds a predetermined quantity (0.3 cc., for example, for a bulb of size and shape known as A19) of ethylsilicate sufficient to properly coat a single bulb. The upper edge of the cup 8 is preferably provided with a flange 12 of suitable shape, here shown as hexagonal, to diffuse oxygen emanating from the holes 11 and produce a uniform steady ame for evenly coating the bulb. The bottom of the burner tube 9 is closed, preferably by a screw (not shown). which may be removed for internal cleaning when necessary` An oxygen feed tube or conduit 13 (FIG. 6) is brazed to the side of the burner tube 9 in communication with the interior thereof. A second air feed tube may also be similarly attached to the burner tube 9 for use, if needed, to introduce a controlled amount of air from the flexible section 9S to the tube 9 during a certain part of the cycle to prevent the burner cup 8 from overheating and thereby maintain it at the desired temperature of to C. at the time the silicate fuel is fed thereto.

The burner 8, 9 is located inside a bulb-supporting spindle 15' which is mounted in bracket 3 for rotation about its axis by a pulley 16 which is driven by a -belt 17 which is wrapped about the pulleys 16 of the several heads and about a drive pulley 18 (FIGS. l and 6) which is attached to a shaft 19 which extends through the hollow column 4 and is rotated from the speed reducer 7. The spindle 15 has a reduced cylindrical upper end 20 (FIG. 3) of a size to snugly receive the reduced neck portion 21 of the glass lamp bulb 22 (FIG. 2) and support it from the shoulder portion 23 of the spindle.

The operation of the coating cycle begins when a head 2 is brought by the turret into operative relation to a silicate fuel dispenser having its nozzle or filler tube 24 (FIGS. 4 and 5) mounted on a cross head or shuttle mechanism shown at A (FIGS. l, 4 and 5) over the path of movement of the heads 2 so that the nozzle 24 shuttles or reciprocates back and forth from cup to cup as they pass by the shuttle. The nozzle 24 is carried by an arm 25 (FIG. 4) which extends laterally from a cross head 26 (FIGS. l, 4 and 5) which slides along a rod 27 supported by a bracket 28 on a stationary frame member 29. Rotation of the cross head 26 is prevented by an upwardly extending arm 30 having a roller 31 riding in a slot or groove in a track member 32 on bracket 28. The cross head 26 is reciprocated through engagement of a lateral arm 33 having a roller 34 engaged by the slotted free end of the vertical arm 35a (FIGS. 4 and 5) of a bell crank lever having a horizontal arm 35h (FIGS. 1 and 5 which is connected at its end to a vertical rod 36 (FIGS. 1, 5 and 6) which is suitably connected at its lower end with a lever 37 (FIG. 6) which is pivoted at 38 and carries a roller 39 engaging the edge cam surface 40 of a cam 41. The timing is such that for a given short period the filler nozzle 24 travels in a straight line at the same speed as the burner cup 8. During this matched speed, the silicate fuel pump 42 (FIG. 6) is cycled to ill a burner cup by actuation of the piston rod 43 of pump 42 by a face cam Igroove (not shown) located in cam 41 and controlling an arm 44 connected to the rod 43. The shuttle or cross head 26 is returned at a faster speed by cam edge so that it can pick up the next burner cup 8 and repeat the till operation. Due to the straight line travel ofthe filler nozzle 24 there is a slight mismatch of ller nozzle to burner cup relationship because the cup is traveling on an arc of large radius. However, the slight difference is insignificant because the arc difference is less than the inside diameter of the cup 8. The pump 42 may be a commercial Bijur oil lubricating pump.

At the moment the silicate fuel charge is fed to a burner cup 8, the said cup is in a lowered position (see FIG. 2) relative to the bulb supporting spindle 15 by virtue of the fact that a roller 45 (FIG. 6) at the lower end of an extensionmember 46 on the burner tube 9 is traversing a low portion of a cam groove 47 in a stationary arcuate cam track 48.

At this lowermost position of the cup 8 the feeding of the bulb 22 onto spindle 15 does not occur until after the cup 8 passes by an ignition burner 50 (FIG. l) which ignites the silicate vapor evolving from the cup 8 and mixing with the oxygen flow through the openings 11 in the burner tube 9; at this time a bulb 22 is directly over the burner and spindle. The oxygen flow to the interior of burner tube 9 is initiated by operation of a valve 51 (FIG. 6) at the periphery of the head-supporting bracket 3 and which is supplied with oxygen from a rotary valve 52 at the axis of the turret 1. The valve 51 is connected to the interior of the burner tube 9 through the tube 13 and conduit 53 including a flexible section 54, and said valve 51 is connected to rotary valve 52 through conduit sections 55. The oxygen ow is triggered by the shifting upwardly of the control pin 56 of valve 51 by a stationary arcuate cam track indicated at 57 and extending along the path of movement of the pin 56.

Immediately after the silicate in burner cup 8 is ig nited, the bulb is lowered onto the rotating spindle 15 at the location indicated by the term Load in FIG. l. The feeding of the endmost bulb 22 on the rails 49 is effected by a star wheel 58 (FIG. l) which segregates the endmost bulb 22 and controls its movement in synchronism with the movement of the spindle on the turret. The

'tendency of the lowermost neck portion 21 of the bulb 22 to tilt back out of alignment with the spindle 15 is prevented by its engagement with the concave face of a guide finger 59 (FIGS. l and 6) associated with and located be low each tooth of the star wheel 58. The nger 59 is pivoted at 60 so it can swing back to permit the larger upper bulbous or bowl portion of the bulb 22 to pass by and drop onto the spindle 15. The linger 59 swings back when a roller 61 on an arm 62 of the pivot pin 6G rolls off a fixed cam 63 located above the star wheel 58. The timed rotation of the star wheel 58 and the bulb guiding fingers 59 is effected by a chain 64 which is wrapped about a sprocket 65 on the supporting shaft 66 for the star wheel and about a drive sprocket 67 on the shaft 19.

After the silicate fuel in burner cup 8 has been ignited and the bulb 22 lowered onto the spindle 15, the burner cup 8 is raised by cam track 48 to its uppermost position with its upper rim at about the same elevation as the maximum diameter of the upper spherical bowl portion of the bulb 22, and during the coating period the cup 8 is lowered and raised, for example about one inch, and four times, to distribute a uniform deposit of silica on the bulb. The final down stroke of the burner cup 8 brings the upper edge thereof at the level of the top of spindle 15 for ease of removal of the bulb. The remaining products of combustion of the ethylsilicate, mainly water vapor and carbon dioxide, are blown out of the bulb downwardly through the annular space between the burner tube 9 and spindle 15.

As herein illustrated7 the burner tube 9 is supported by a spaced pair of pivoting arms 68 (FIG. 6) which are supported from the bracket 3 so that the tube oscillates vertically `with a parallel arc motion, there being sufficient spacing between the burner tube 9, and the interior of spindle 15 to permit such a motion. This motion tends to assist in maintaining the spindle 15 and tube 9 free from deposits of silica carried therethrough along with the other products of combustion.

Immediately following placement of the bulb 22 on the spindle 15, they are carried past a bank of fires from a series of burners 69 which are mounted along the path of travel of the heads 2. These burners 69 perform a dual function. In addition to minimizing thermal shock to the bulb by balancing the intense heat generated inside the bulb by the combustion of the ethylsilicate in the cups 8, the said burners 69 are so directed as to maintain proper temperature of the cups 8. In case a bulb 22 should not be loaded on a given head for some reason, the cup 8 on that head would then cool sufficiently so that when a bulb is next loaded on that head the temperature of the cup 8 would be too low to effectively volatilize the ethylsilicate for total combustion, thereby resulting in an unacceptably thin coating of silica. In the event of such absence of a bulb, the lires 69 maintain the cup at the proper temperature. The cups 8 are ordinarily maintained at proper temperature by the entrapment of the intense heat of the silicate llame due to the presence of the enclosing bulb 22.

The bulbs 22 and spindles 15' are continuously rotated about their common axis by the belt 17 engaging the pulleys 16 on the spindles. It may be noted that portions of the belt 17 extending inwardly of the turret to and from the drive pulley 18 (FIG. l) do not interfere with the legs 70 (FIG. 5) of the support 71 for the rotary valve 52 which is located directly above the pulley 18, because the said portions of belt 17 and the legs 70 are parts of the rotating combination. The upper half 72 of the rotary valve 52 is the stationary part and is connected to a portion of a stationary frame by a bar 73 which extends across the turret.

After the charge of silicate in the burner cup 8 has completely burned, the flow of oxygen through the burner tube 9 and holes 11 is stopped when the control pin 56 of valve 51 (FIG. 6) passes under a cam track (not shown) which pushes the pin 56 downward. The head 2 carrying the bulb 22 also passes beyond the last of the series of burners 69 after which the bulb is removed from the head.

After the coating cycle has been completed the bulb is removed from the head 2 as it approaches the up wardly inclined forward portions of a pair of rails 74 (FIG. l) and is pushed upward by a stripper plate 75 (FIG. 6) into the path of a tooth on a second star wheel 76 (FIG. 1).

The stripper plate 75 is carried by a rod 77 (FIG. 6) which is supported by a pair of pivot arms 78 from the bracket 3 and carries at its lower end a roller 79 which is controlled by a stationary arcuate cam track 80 which causes the rod 77 to move upward and carry the stripper plate into engagement with the bottom of the bulb 22 and lift it ofiF the spindle 15. The bulb 22 is pushed up the forward portion of the rails 74 by one of the teeth of the star wheel 76 to a high point of the rails from which it slides along a downwardly inclined portion of the rails from which it is discharged, for example, to a conveyor belt (not shown). The star wheel 76 may also be rotated by the chain 64 engaging a sprocket 81 which is mounted on a shaft 82 which also carries the star Wheel 76 and is, in turn, carried by a frame member 83 above the turret.

After removal of the bulb 22 from the head 2, the spindle and burners 8, 9 engage a group of brushes 100e, b and c (FIG. 8) that removes and prevent an accumulation of silica powder thereon. As illustrated in FIG. 8 a pair of brushes 100e and 10011 are of circular shape and are xedly mounted from a frame member 101 at the periphery of the turret heads 3 to be at opposite sides of the burner 8, 9, and a xed brush 100C is mounted to engage the upper end of the rotating spindle 15. The interior of the burner cup 8 is then cleaned of a residue of ash or sludge by one of a series of spherical files or reamers 84 (FIGS. 1 and 7) on the ends of spindles 85 which project radially from a vertical turret 86 above the path of movement of the heads 2. The rotation of the turret 86 is timed so that successive rotary files 84 enter successive cups 8 and scrub out the interior to remove the ash therein which would otherwise accumulate and soon clog the cups. The turret 86 is rotated by the chain 64 through a sprocket 87 on a vertical shaft 88 which carries a bevel gear 89 which meshes with a bevel gear 90 carried by the shaft 91 which supports the turret 86. The files or reamers 84 are continuously rotated by a separate electric motor and speed reducer drive 92 (FIG. 1) which rotates a large common bevel gear 93 (FIG. 7) which drives the individual bevel gears 94 on the spindles S5 carrying the reamers 84. After each burner cup 8 is scrubbed, the loosened residue of ash is blown out by an air jet (not shown) directed into the interior of the cup.

The heat dissipating capacity of the burners 8, 9 is such that the heat supplied thereto by the burning of the silicate fuel and by the burners 69 is such that the heat retained by the cups 8 at the time the silicate fuel is fed thereto in the next cycle of operation, is sufficient to maintain the cups within the desired temperature range of 110 to 135 C. for proper volatilization and combustion of the silicate fuel. Howeevr, in the event that the cups S should be running at a temperature exceeding about 135 C., they may be cooled in any appropriate manner. As herein illustrated, cooling of the cups S may be effected by applying a flow of compressed air to the interior of the burner tube 9 through the conduit (FIG. 6) by way of additional conduit including a exible section 95, connected to the second control valve 96 (FIG. 6) at the outer edge of bracket 3 and which is supplied with compressed air through conduits 97 connected to appropriate passages in the rotary valve 52. The valve 96 is actuated by engagement of its control pin 98 with an arcuate stationary cam track indicated at 99 and which may extend along the path of the pin 98 for some distance back from the location at which the silicate fuel is fed to the burner cup 8. The valve 96 is again operated to shut off the air flow before the next coating cycle is started.

However, in actual operation of a machine of the type shown and described herein it has not been necessary to cool the cups 8, so that cooling air has not been supplied to the burners. In the unlikely event that a particular design of machine should result in the cups 8 running below a temperature of about 110 C., it is evident that burners may be located along their path of travel to the fuel feeding location to bring their temperature up to that level.

In FIG. 9, there is shown an alternative mode of r0- tating the bulb-supporting spindles 15 whereby the spindles are not rotated during loading of the bulbs thereon, and preferably also are not rotated during unloading of the bulbs therefrom. To that end, the belt 17 of FIG. 1

6 is replaced by a belt 17b (FIG. 9) which has gear-like teeth 102 on its inner face and which mesh with cooperating teeth on the pulleys on sprockets 16b which are attached to the spindles 15.

The belt 17b is driven from a drive sprocket 103 from a separate electric motor 104. An idler pulley 105 is so arranged that the belt 1711 is held out of contact with the sprockets 16h which are located at the station bearing the legend Load, as well as the sprockets at the two preceding stations. Thereby, when a bulb is loaded onto the spindle 15 at the loading station, that spindle is no longer rotating about its axis.

Similarly, another idler sprocket 105 is so arranged that the belt 17b is held out of engagement with the sprockets 16b which are located at the station bearing the legend Unload, as well as the sprockets 16h irnmediately preceding and succeeding that station. Thereby the spindle 15 is not rotating when it is unloaded therefrom onto the rails 74 by the star wheel 76 shown in FIG. 1.

While a particular embodiment has been specifically shown and described herein, it will be evident to those skilled in the a-rt that certain changes, modifications and omissions may be made within the spirit and scope of the invention as defined inthe appended claims.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. In apparatus f-or coating the interior of glass electric lamp bulbs with silica deposited thereon by combustion of a liquid ethylsilicate compound, the combination of a rotary turret having at its periphery a plurality of equidistantly spaced heads, each said head comprising means to support a lamp bulb with its open neck end lowermost and burner means including a fuel cup arranged relative to said bulb holder means to be located within a bulb held by said holder means, burner support means holding said Cup and including means to supply an upward ow of oxygen gas around said fuel cup during rotation of the turret, means adjacent the path of movement of said heads to supply a predetermined quantity of liquid silicate compound to individual fuel cups during rotation of the turret, means to initiate flow of oxygen around said cup, an ignition burner means mounted adjacent said turret further along the path of movement of said heads and in a position to direct a arne toward a fuel cup moving thereacross to ignite vapor of said silicate compound evolving from said fuel cup preparatory to placement of a bulb in said bulb holder means, means to effect cessation of said flow of oxygen at a location sufficiently further alo-ng the path of movement of said heads that the supply of silicate fuel has been consumed, supplemental burner means arranged at close intervals along the path of movement of said heads from a location immediately beyond that at which the said ignition burner is located to a location beyond that at which cessation of oxygen ow is effected, said supplemental burner means bei-ng directed toward the exterior of bulbs in heads passing thereby and also directed toward fuel cups passing thereby in the absence of bulbs in said heads, the heat dissipating capacity of each of said cups and its support means being correlated with heat supplied thereto and dissipated therefrom such that said cups are at a temperature in the range of about 11G-135 C. at the time the silicate fuel is supplied thereto whereby to assure proper volatilization of the silicate fuel for ready ignition and uniform combustion thereof.

2. Apparatus as set forth in claim 1 wherein the said bulb support means is a hollow vertical spindle having its upper end arranged to snugly receive the neck of said bulb, the burner support means is a hollow tube closed at both ends and arranged to extend longitudinally through said spindle, the fuel cup is mounted on the upper end -of said tube, and said upper end of the tube is provided with small apertures arranged around and closely adjacent the periphery of the cup and communicating with the hollow interior of said tube, and the oxygen supply means includes a conduit connected with the interior of said tube, and means are provided to support said burner tube and to reciprocate it vertically during the period of combustion of the silicate fuel in said cup.

3. Apparatus as set forth in claim 2 wherein the upper edge of the fuel cup is provided with a flange which diffuses the oxygen issuing from the apertures in the end of said burner tube.

4. Apparatus as set forth in claim 1 including reamer means mounted above the path of travel of said cups, and means to rotate said reamers and to move them in timed Vrelationship to the movement of the cups to enter the cups and scrub the interior thereof.

5. Apparatus as set forth in claim 1 wherein a plu- 3/1951 Pipkin 118-48 X 6/1954 Kuebzer 118-48 CHARLES A. WILLMUTH, Primary Examiner.

I. P. MCINTOSH, Assistant Examiner. 

1. IN APPARATUS FOR COATING THE INTERIOR OF GLASS ELECTRIC LAMP BULBS WITH SILICA DEPOSITED THEREON BY COMBUSTION OF A LIQUID ETHYLSILICATE COMPOUND, THE COMBINATION OF A ROTARY TURRET HAVING AT ITS PERIPHERY A PLURALITY OF EQUIDISTANTLY SPACED HEADS, EACH SAID HEAD COMPRISING MEANS TO SUPPORT A LAMP BULB WITH ITS OPEN NECK END LOWERMOST AND BURNER MEANS INCLUDING A FUEL CUP ARRANGED RELATIVE TO SAID BULB HOLDER MEANS TO BE LOCATED WITHIN A BULB HELD BY SAID HOLDER MEANS, BURNER SUPPORT MEANS HOLDING SAID CUP AND INCLUDING MEANS TO SUPPLY AN UPWARDLY FLOW OF OXYGEN GAS AROUND SAID FUEL CUP DURING ROTATION OF THE TURRET, MEANS ADJACENT THE PATH OF MOVEMENT OF SAID HEADS TO SUPPLY A PREDETERMINED QUANTITY OF LIQUID SILICATE COMPOUND TO INDIVIDUAL FUEL CUPS DURING ROTATION OF THE TURRET, MEANS TO INITIATE FLOW OF OXYGEN AROUND SAID CUP, AN IGNITION BURNER MEANS MOUNTED ADJACENT SAID TURRET FURTHER ALONG THE PATH OF MOVEMENT OF SAID HEADS AND IN A POSITION TO DIRECT A FLAME TOWARD A FUEL CUP MOVING THEREACROSS TO IGNITE VAPOR OF SAID SILICATE COMPOUND EVLOVING FROM SAID FUEL CUP PREPARATORY TO PLACEMENT OF A BULB IN SAID BULB HOLDER MEANS, MEANS TO EFFECT CESSATION OF SAID FLOW OF OXYGEN AT A LOCATION SUFFICIENTLY FURTHER ALONG THE PATH OF MOVEMENT OF SAID HEADS THAT THE SUPPLY OF SILICATE FUEL HAS BEEN CONSUMED, SUPPLEMENTAL BURNER MEANS ARRANGED AT CLOSE INTERVALS ALONG THE PATH OF MOVEMENT OF SAID HEADS FROM A LOCATION IMMEDIATELY BEYOND THAT AT WHICH THE SAID INGITION BURNER IS LOCATED TO A LOCATION BEYOND THAT AT WHICH CESSATION OF OXYGEN FLOW IS EFFECTED, SAID SUPPLEMENTAL BURNER MEANS BEING DIRECTED TOWARD THE EXTERIOR OF BULBS IN HEADS PASSING THEREBY AND ALSO DIRECTED TOWARD FUEL CUPS PASSING THEREBY IN THE ABSENCE OF BULBS IN SAID HEADS, THE HEAT DISSIPATING CAPACITY OF EACH OF SAID CUPS AND ITS SUPPORT MEANS BEING CORRELATED WITH HEAT SUPPLIED THERETO AND DISSIPATED THEREFROM SUCH THAT SAID CUPS ARE AT A TEMPERATURE IN THE RANGE OF ABOUT 110-135* C. AT THE TIME THE SILICATE FUEL IS SUPPLIED THERETO WHEREBY TO ASSURE PROPER VOLATILIZATION OF THE SILICATE FUEL FOR READY IGNITION AND UNIFORM COMBUSTION THEREOF. 